Hydrophilic-oleophobic copolymer composition and uses thereof

ABSTRACT

Provided herein are copolymers and copolymer compositions that are both hydrophilic and oleophobic. The copolymers include structural units derived from a fluoroalkyl monomer and a zwitterionic monomer. It further relates to membranes formed by coating a porous substrate with the copolymeric compositions. The copolymeric coating imparts hydrophilicity and oleophobicity/oil-tolerance to the membranes. The uses of such membranes as microfiltration membrane or ultrafiltration membrane are also provided.

FIELD OF INVENTION

The disclosure generally relates to copolymers and copolymercompositions that are both hydrophilic and oleophobic. It furtherrelates to membranes coated with such copolymer compositions to impartboth hydrophilicity and oleophobicity to the membranes and their uses,for example, as filtration membranes for treatment ofhydrocarbon-containing water.

BACKGROUND

Efficient removal of oily suspended solids (e.g., oil-coated dirtparticles) from water is one of the major challenges in water-treatmentindustry. For example, large-scale methods for treatment ofhydrocarbon-containing waste water (e.g., oil-containing water) in apetroleum industry may range from giant containment booms and absorbentskimmers to chemical treatments. Produced water from unconventional gasproduction are often disposed of by underground injection. Prior to itsdisposal, the produced water is treated with significant levels ofbiocide to prevent fouling of the disposal well. Some of theseconventional water-treatment techniques have questionable effects onhuman health and environment.

Filtration methods could provide a more efficient and scalable approachfor treatment of hydrocarbon-containing water and to remove oilysuspended particles. Microbial removal by microfiltration has potentialto be a lower cost option than biocide treatment. However, formicrofiltration to be less expensive than biocide treatment, themicrofilter must be hydrophilic and not be fouled by oils present in theproduced water. Ceramic membranes that are oil-tolerant have beenemployed for treatment of oil-containing water. However, ceramicmembranes have significant disadvantages in terms of their higher weightand production costs. Further, ceramic membranes have significantlimitations in application areas where oily suspended solids are to beremoved from contaminated water.

Polymeric membranes are suitable candidates for water treatmentprocesses. Polymeric membranes are cheaper in comparison with theirceramic counter parts and are also more compact. The use of polymericmembranes for treating water reduces the operating cost and size ofwater-treatment plants employing the same. However, one of the majordrawbacks of polymeric membranes is membrane fouling. Generally,membrane fouling occurs when impurities in water such as emulsified,free, or dissolved oil are irreversibly deposited on the membranesurface and/or within the internal pores of the membrane. These depositsnot only decrease the membrane lifetime but also lead to a dramaticreduction in water flux, subsequently leading to an increased operatingcosts. Additionally, if a polymeric membrane is not hydrophilic innature, aqueous dispersions such as oil-containing waste water cannot bereadily filtered through these membranes without pre-wetting themembrane with organic solvents such as isopropanol followed by flushingwith water to overcome the lack of affinity between the non-hydrophilicmaterial and the polar aqueous dispersion. Such pre-wetting of membranesmay be expensive and may also lead to “gas-lock” or “de-wetting”.

In view of the above, there remains a need for development ofhydrophilic polymeric membranes that are both oleophobic andoil-tolerant so as to enable their use in treatment ofhydrocarbon-contaminated water without being rapidly fouled byhydrocarbons.

BRIEF DESCRIPTION OF THE INVENTION

The invention is directed to copolymers and copolymeric compositionsthat are both hydrophilic and oleophobic. Membranes comprising suchcopolymeric compositions, which are both hydrophilic and oleophobicand/or oil-tolerant are also provided.

In some embodiments, a copolymer comprising 1 to 50 mole % of astructural unit of formula I and 25 to 99 mole % of a structural unit offormula II are provided.

In formulas I and/or II, R¹ is a linear or branched C₁-C₃₀ fluoroalkylgroup. R² and R³ are independently at each occurrence a hydrogen, or alinear or branched C₁-C₄ alkyl group. In some embodiments, R⁴ and R⁵ areindependently at each occurrence a linear or branched C₁-C₁₂ alkylgroup, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclic group; andR⁶ and R⁷ are independently at each occurrence a linear or branchedC₁-C₁₂ alkylene group, a linear or branched C₂-C₁₂ alkenylene group, alinear or branched C₂-C₁₂ alkylnlene group, a C₅-C₁₂ carbocyclic group,or a C₅-C₁₂ heterocyclic group. In some other embodiments, at least twoof R⁴, R⁵, R⁶, or R⁷ together with the nitrogen atom to which they areattached may form a heterocyclic ring containing 5 to 7 atoms. X isindependently at each occurrence either an oxygen atom (—O—) or an —NH—group; and Y is either a sulfite group or a carboxylate group. Thevalues of m and n are independently at each occurrence an integerranging from 1 to 5.

In some embodiments, a copolymer comprising structural units derivedfrom a mixture of ethylenically unsaturated monomers comprising 1 to 50mole % of fluoroalkyl monomer of formula III and 25 to 99 mole % ofzwitterionic monomer of formula IV is provided.

In formulas II and/or IV, R¹ is a linear or branched C₁-C₃₀ fluoroalkylgroup. R² and R³ are independently at each occurrence a hydrogen, or alinear or branched C₁-C₄ alkyl group. In some embodiments, in formulaIV, R⁴ and R⁵ are independently at each occurrence a linear or branchedC₁-C₁₂ alkyl group; a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclicgroup; and R⁶ and R⁷ are independently at each occurrence a linear orbranched C₁-C₁₂ alkylene group, a linear or branched C₂-C₁₂ alkenylenegroup, a linear or branched C₂-C₁₂ alkylnlene group, a C₅-C₁₂carbocyclic group, or a C₅-C₁₂ heterocyclic group. In some otherembodiments, at least two of R⁴, R⁵, R⁶, or R⁷ of formula IV togetherwith the nitrogen atom to which they are attached form a heterocyclicring containing 5 to 7 atoms. X is independently at each occurrenceeither an oxygen atom (—O—) or an —NH— group; and Y is an anionic group.The values of m and n are independently at each occurrence an integerranging from 1 to 5.

In some embodiments, a composition comprising any of the above-disclosedcopolymers is provided. In some embodiments, the copolymer comprises 1to 50 mole % of a structural unit of formula VII, and 25 to 99 mole % ofa structural unit of formula VIII, wherein R¹ is a linear C₅-C₈fluoroalkyl group.

In some embodiments, a membrane comprising a porous substrate andoptionally a coating attached to the porous substrate is provided,wherein at least one of the porous substrate or the coating comprisesany of the above-disclosed copolymers or copolymeric compositions. Insome embodiments, the polymeric composition comprises a copolymercomprising 1 to 50 mole % of a structural unit of formula VI, and 25 to99 mole % of a structural unit of formula VII, wherein R¹ is a linearC₅-C₈ fluoroalkyl group.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings.

FIG. 1 shows a transmission electron microscopic (TEM) picture of z90copolymer-coated ePTFE/PTFE membrane.

FIG. 2 shows contact angles of a hydrocarbon and water on an ePTFE/PTFEmembrane coated with z90 copolymer.

FIG. 3 illustrates the measured flux characteristics of a z90copolymer-coated ePTFE/PTFE membrane in comparison with an ePTFE/PTFEmembrane without any copolymer coating.

DETAILED DESCRIPTION

The invention is directed to hydrophilic-oleophobic copolymers andmembranes formed therefrom. It further relates to the uses ofcopolymeric compositions as coating materials on porous substrates toform filtration membranes having both hydrophilic and oleophobicproperties. By incorporating both hydrophilicity and oleophobicity to afiltration membrane, such coating enables efficient filtration ofhydrocarbon-contaminated water, for example, filtration of producedwater to remove suspended oily particles. In absence of such coatings,hydrocarbons (e.g., as emulsified, dissolved, or free oil in producedwater) may rapidly foul a filtration membrane. Oleophobicity andoil-tolerance imparted by such copolymer coating may prevent oil in thecontaminated water from wetting the membrane, occluding its pores, andstopping the filtration. Further, enhanced hydrophilicity may allowpassage of water through these filtration membranes without the need forprior pre-wetting the filtration membrane with solvents such asisopropanol. Thus the filtration membrane having such coatings may beeffectively used for treatment of contaminated water(hydrocarbon-containing water) with less frequent cleaning requirements.Such filtration membranes also obviate the need of chemical treatmentfacilities, and in turn reduce the need of usage, handling and storageof environmentally harmful toxic chemicals (e.g. biocides and solvents)in field operations.

To more clearly and concisely describe and point out the subject matterof the claimed invention, the following definitions are provided forspecific terms, which are used in the following description and theappended claims.

As used herein, the term “acyclic” refers to a compound/group which doesnot contain a ring. The term acyclic atom refers to an atom which is nota ring member.

As used herein, the term “alicyclic” refers to a compound/group thatcontains non-aromatic ring(s). Alicyclic system includes polycyclic ringsystems, which does not have an aromatic ring (e.g., benzene) as one ofthe cyclos. The term “cyclo” denotes a ring of a polycyclic ring system.As used herein the term “aromatic” refers to a compound/group having atleast one aromatic ring. It also includes polycyclic ring system havingat least one aromatic ring (e.g., a benzene ring) as one of the cyclos.Ring systems in general include substituted rings, includingsubstitution in the form of additional fused or bridged ring(s).

As used herein, the term “alkyl group” refers to an acyclic carbon or asaturated acyclic carbon chain represented by the formula,—C_(n)H_(2n+1).

As used herein, the term “alkylene group” refers an acyclic carbon or asaturated acyclic carbon chain represented by the formula,—(C_(n)H_(2n))—.

As used herein, the term “alkenyl group” refers to an acyclic carbonchain that contains a carbon-to-carbon double bond, and is representedby the formula, —C_(n)H_(2n−1).

As used herein, the term alkenylene group refers to an acyclic carbonchain that contains a carbon-to-carbon double bond, and is representedby the formula, —(C_(n)H_(2n−2))—.

As used herein, the term “alkynyl group” refers to an acyclic carbonchain that contains a carbon-to-carbon triple bond, and is representedby the formula, —C_(n)H_(2n−3).

As used herein, the term “alkynlene group” refers to an acyclic carbonchain that contains a carbon-to-carbon triple bond, and is representedby the formula, —(C_(n)H_(2n-4))—.

As used herein, the term “fluoroalkyl group” refers to an alkyl groupwherein at least one of the hydrogen atoms of the alkyl group issubstituted by a fluorine atom. The fluoroalkyl group includes, but notlimited to, a perfluorinated alkyl group, wherein all hydrogen atoms ofan alkyl group are substituted with fluorine atoms.

As used herein, the term “carbocyclic group” refers to chemical moietiescomprising at least one carbocyclic ring. The term “carbocyclic ring”denotes a ring or ring system where all the ring members are carbons.The carbocyclic groups may be an alicyclic group (e.g., cycloalkylgroups such as cyclohexane group or cyclopentane group) or an aromaticgroup (e.g., a benzyl group, a benzene group, a naphthalene group or ananthracene group). The carbocyclic groups may be substituted orun-substituted.

As used herein, the term “heterocyclic group” refers chemical unitscomprising at least one hetero ring. The term “hetero ring” denotes aring having carbon and at least one atom from the group consisting ofnitrogen, oxygen, sulfur, selenium and tellurium as ring members, andcontains no other element as a ring member. To qualify as hetero ring,non-ionic bonding must exist between all ring members. Inner saltcompounds such as betaines, sufobetaines etc., wherein two ring membersare attached to each other by ionic bonding are not regarded as heterorings. The heterocyclic groups/rings may be alicyclic (e.g., apiperidine group) or aromatic (e.g., a pyrrole group, a pyridine group).The heterocyclic groups/rings may be substituted (e.g., 2-methylpyridinegroup) or un-substituted.

As used herein, a coated membrane is referred as “oil-tolerant” if theperformance of the coated membrane in an oil-containing feed is the same(or within acceptable operable limits) as the performance of an uncoatedmembrane in an oil-free feed stream. For example, theperformance/behavior of an oil-tolerant system may not changedramatically when oil is introduced into the system. For example, withan oil-tolerant coated membrane, flux of clean water or brine may behigh, but flux through an uncoated membrane may degrade rapidly when thefeed contains oil.

As used herein, a material with a measured contact angle of water orbrine <20° is referred to be hydrophilic, while a material with ameasured contact angle of hexane or hexadecane >60° is referred to beoleophobic.

In some embodiments, a copolymer comprising structural units havingformula I and formula II are provided.

In formula I, R¹ may be a linear or branched C₁-C₃₀ fluoroalkyl groupand R² may be a hydrogen, or a linear or branched C₁-C₄ alkyl group. Informula II, R³ may be a hydrogen, or a linear or branched C₁-C₄ alkylgroup. Y is an anionic group. For example, Y may be a sulfite group(—SO₃ ⁻) or a carboxylate (—CO₂ ⁻) group. In formulas I and II, X maybe, independently at each occurrence, an oxygen atom (—O—) or an —NH—group, and the values of m and n are, independently at each occurrence,an integer ranging from 1 to 5. In some embodiments, R⁴ and R⁵ informula II are, independently at each occurrence, a linear or branchedC₁-C₁₂ alkyl group, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclicgroup; and R⁶ and R⁷ are independently at each occurrence a linear orbranched C₁-C₁₂ alkylene group, a linear or branched C₂-C₁₂ alkenylenegroup, a linear or branched C₂-C₁₂ alkylnlene group, a C₅-C₁₂carbocyclic group, or a C₅-C₁₂ heterocyclic group. R⁴, R⁵, R⁶, or R⁷ maybe substituted or un-substituted. For example, R⁴, R⁵, R⁶, or R⁷ may besaccharide which has hydroxyl substitution. In some other embodiments,R⁴, R⁵, R⁶, or R⁷ may be such at least two of R⁴, R⁵, R⁶, or R⁷ togetherwith the nitrogen atom to which they are attached form a heterocyclicring containing 5 to 7 atoms. For example, in some embodiments, R⁴ andR⁵ together with the nitrogen atom to which they are attached may forman imidazole structure. The formed heterocyclic ring may be an aliphaticring or an aromatic ring. In some embodiments, when at least two of R⁴,R⁵, R⁶, or R⁷ are connected together along with the nitrogen atom towhich they are attached may generate a substituted heterocyclic ring.

In some embodiments, a copolymer comprising 1 to 50 mole % of astructural unit of formula I and 25 to 99 mole % of a structural unit offormula II is provided. In some embodiments, a copolymer comprising 1 to49 mole % of a structural unit of formula I and 25 to 99 mole % of astructural unit of formula II is provided. In some other embodiments, acopolymer is provided that comprises 1 to 30 mole % of a structural unitof formula I and 25 to 99 mole % of a structural unit of formula II. Insome other embodiments, a copolymer comprising 1 to 29 mole % of astructural unit of formula I and 71 to 99 mole % of a structural unit offormula II is provided. In some other embodiments, a copolymer isprovided that comprises 1 to 25 mole % of a structural unit of formula Iand 75 to 99 mole % of a structural unit of formula II. In some exampleembodiments, a copolymer comprising 1 to 10 mole % of a structural unitof formula I and 90 to 99 mole % of a structural unit of formula II isprovided. In any of the above embodiments, R¹ is a linear or branchedC₁-C₃₀ fluoroalkyl group; R² and R³ are independently at each occurrencea hydrogen, or a linear or branched C₁-C₄ alkyl group; X isindependently at each occurrence an oxygen atom (—O—) or an —NH— group;Y is a sulfite (—SO₃ ⁻) group or a carboxylate (—CO₂ ⁻) group. Thevalues of m and n are independently at each occurrence an integerranging from 1 to 5. In some embodiments, R⁴ and R⁵ are independently ateach occurrence a linear or branched C₁-C₁₂ alkyl group, a C₅-C₁₂carbocyclic group, or a C₅-C₁₂ heterocyclic group; and R⁶ and R⁷ areindependently at each occurrence a linear or branched C₁-C₁₂ alkylenegroup, a linear or branched C₂-C₁₂ alkenylene group, a linear orbranched C₂-C₁₂ alkylnlene group, a C₅-C₁₂ carbocyclic group, or aC₅-C₁₂ heterocyclic group. In some other embodiments, R⁴, R⁵, R⁶, or R⁷are such at least two of R⁴, R⁵, R⁶, or R⁷ together with the nitrogenatom to which they are attached form a heterocyclic ring containing 5 to7 atoms.

The structural units of formula I that contains the fluoroalkyl groupimpart oleophobicity and structural units of formula II that containsthe zwitterionic group impart hydrophilicity to the copolymer. Thus thecopolymer comprising the structural units of formula I and formula II isboth hydrophiplic and oleophobic.

The carbon backbone of the fluoroalkyl groups may be linear or branched.The fluoroalkyl groups may include cyclic structures as well. It mayalso include one or more heteroatoms other than fluorine (e.g.,nitrogen, oxygen or sulfur atom(s)). The fluoroalkyl group may be apartially fluorinated group (e.g., —CHF₂—) or a perfluorinated group(e.g., —CF₃). In some embodiments, the fluoroalkyl group may be a C₃-C₁₅fluoroalkyl group. In some other embodiments, the fluoroalkyl group maybe a C₆ fluoroalkyl group. Non-limiting examples of suitable fluoroalkylgroups include, but are not limited to, trifluoromethyl,pentafluoroethyl, nonafluorobutyl, tridecafluorohexyl,hexadecafluorooctyl, 2,2,2-trifluoroethyl, 3,3,3,2,2-pentafluoropropyl,5,5,5,4,4,3,3,2,2-nonafluoropentyl,7,7,7,6,6,5,5,4,4,3,3,2,2-tridecafluoroheptyl,9,9,9,8,8,7,7,6,6,5,5,4,4,3,3,2,2-hexadecafluorononyl,1,2-dihydroperfluorocyclopentane or 1,1,2-trihydroperfluorocyclopentane.In one example embodiment, the fluoroalkyl group of formula I is atridecafluoro hexyl group.

Referring to formulas I and II, R² and R³ may be independently at eachoccurrence a hydrogen, or a linear or branched C₁-C₄ alkyl group. Forexample, R² and R³ may be independently at each occurrence a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, an isobutyl group, a secondary butyl group or a tertiary butylgroup. In one example embodiment, both R² and R³ may be a methyl group.

In some embodiments, R⁴ and R⁵ are independently at each occurrence alinear or branched C₁-C₁₂ alkyl group, a C₅-C₁₂ carbocyclic group, or aC₅-C₁₂ heterocyclic group. In some example embodiments, R⁴ and R⁵ may beindependently at each occurrence a linear or branched C₁-C₄ alkyl group,for example, a methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, an isobutyl group, a secondary butylgroup, or a tertiary butyl group. In one example, each R⁴ and R⁵ ismethyl group.

In some embodiments, R⁶ and R⁷ are independently at each occurrence alinear or branched C₁-C₁₂ alkylene group, a linear or branched C₂-C₁₂alkenylene group, a linear or branched C₂-C₁₂ alkylnlene group, a C₅-C₁₂carbocyclic group, or a C₅-C₁₂ heterocyclic group. In some exampleembodiments, R⁶ and R⁷ may be independently at each occurrence a linearor branched C₁-C₄ alkyl group, for example, a methylene group, anethylene group, a propylene group, an isopropylene group, a butylenegroup, an isobutylene group, a tertiary butylene group. In one example,each R⁶ and R⁷ is methylene group.

In some other embodiments, R⁴, R⁵, R⁶, or R⁷ may be such that at leasttwo of R⁴, R⁵, R⁶, or R⁷ together with the nitrogen atom to which theyare attached form a heterocyclic ring containing 5 to 7 atoms. Theheterocyclic ring formed may or may not be an aromatic ring. Further, itmay be a substituted heterocyclic ring or an un-substituted heterocyclicring. For example, R⁴, R⁵ may, together with nitrogen atom, form apiperidine type of structure (e.g., structure I), or R⁴, R⁵, and R⁶together with nitrogen atom may form structures such as structure II, orR⁵, and R⁷ together with nitrogen atom may form structures such asstructure III.

In some embodiments, values of m and n may independently at eachoccurrence an integer range from 1 to 5. In some example embodiments,values of m and n may independently range from 1 to 4, 1 to 3, or 1 to2. In one example embodiment, the value of both m and n may be 1.

In some embodiments, a copolymer comprising 1 to 50 mole % of astructural unit of formula I and 25 to 99 mole % of a structural unit offormula II is provided. The copolymer may further comprise structuralunits other than formula I and formula II. The maximum mole % of suchother additional structural units may be derived from the formula100−(1+25)=74. For example, in some embodiments, the copolymer mayfurther comprise 0 to 74 mole % of additional structural units apartfrom the structural units of formula I and formula II. The additionalstructural units may be derived from a crosslinker, a structural unitthat impart stability, a structural unit that further imparthydrophilicity, a structural unit that further impart oleophobicity, astructural unit that impart both hydrophilicity and oleophobicity, or astructural unit that further impart hydrophobicity. For example, in someembodiments, the copolymer may comprise 30 mole % of formula I, 69 mole% of formula II and 1 mole % of a structural unit derived from a crosslinker.

In some embodiments, the copolymer comprises 1 to 30 mole % of thestructural unit of formula I and 25 to 99 mole % of the structural unitof formula II. The copolymer may further comprise 0 to 74 mole % ofadditional structural units apart from the structural units of formula Iand formula II. In some other embodiments, the copolymer comprises 1 to29 mole % of the structural unit of formula I; and 71 to 99 mole % ofthe structural unit of formula II. In such embodiments, the copolymermay further comprise 0 to 28 mole % of additional structural units inaddition to the structural units of formula I and formula II. In someexample embodiments, the copolymer comprises 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II. In these embodiments, the copolymer may further comprise0 to 24 mole % of structural units other than that of formula I andformula II.

In some embodiments, a copolymer that comprises 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II, is provided, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a linear or branched C₁-C₄ alkyl group; X is independentlyat each occurrence an —O— or —NH—; Y is a sulfite group or a carboxylategroup. The values of m and n are independently at each occurrence aninteger ranging from 1 to 5. In some example embodiments, R⁴ and R⁵ ofthe copolymer may be independently at each occurrence a linear orbranched C₁-C₁₂ alkyl group, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂heterocyclic group; and R⁶ and R⁷ of the copolymer may be independentlyat each occurrence a linear or branched C₁-C₁₂ alkylene group, a linearor branched C₂-C₁₂ alkenylene group, a linear or branched C₂-C₁₂alkylnlene group, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclicgroup. In some other example embodiments, R⁴, R⁵, R⁶, or R⁷ may beidentified such at least two of R⁴, R⁵, R⁶, or R⁷ together with thenitrogen atom to which they are attached form a heterocyclic ringcontaining 5 to 7 atoms.

In some embodiments, a copolymer is provided, which comprises 1 to 25mole % of the structural unit of formula I and 75 to 99 mole % of thestructural unit of formula II, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a methyl group; X is independently at each occurrence an—O— or —NH—; Y is a sulfite group or a carboxylate group. The values ofm and n are independently at each occurrence an integer ranging from 1to 5. In some example embodiments, R⁴ and R⁵ of the copolymer may beindependently at each occurrence a linear or branched C₁-C₁₂ alkylgroup, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclic group; andR⁶ and R⁷ of the copolymer may be independently at each occurrence alinear or branched C₁-C₁₂ alkylene group, a linear or branched C₂-C₁₂alkenylene group, a linear or branched C₂-C₁₂ alkylnlene group, a C₅-C₁₂carbocyclic group, or a C₅-C₁₂ heterocyclic group. In some other exampleembodiments, R⁴, R⁵, R⁶, or R⁷ may be identified such at least two ofR⁴, R⁵, R⁶, or R⁷ together with the nitrogen atom to which they areattached form a heterocyclic ring containing 5 to 7 atoms.

In some embodiments, a copolymer that comprises 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II is provided, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a methyl group; X is independently at each occurrence an—O— or —NH—; Y is a sulfite group or a carboxylate group. The values ofm and n are independently at each occurrence an integer ranging from 1to 5. R⁴ and R⁵ are independently at each occurrence a linear orbranched C₁-C₃ alkyl group; and R⁶ and R⁷ are independently at eachoccurrence a linear or branched C₁-C₁₂ alkylene group, a linear orbranched C₂-C₁₂ alkenylene group, a linear or branched C₂-C₁₂ alkylnlenegroup, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclic group.

In some embodiments, a copolymer that comprises 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II is provided, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a methyl group; X is independently at each occurrence an—O— or —NH—; Y is a sulfite group or a carboxylate group. The values ofm and n are independently at each occurrence an integer ranging from 1to 5. R⁴ and R⁵ are independently at each occurrence a linear orbranched C₁-C₃ alkyl group; and R⁶ and R⁷ are independently at eachoccurrence a linear or branched C₁-C₅ alkylene group.

In some embodiments, a copolymer that comprises 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II is provided, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a methyl group; X is an —O—; Y is a sulfite group or acarboxylate group. The values of m and n are independently at eachoccurrence an integer ranging from 1 to 5. R⁴ and R⁵ are independentlyat each occurrence a linear or branched C₁-C₃ alkyl group; and R⁶ and R⁷are independently at each occurrence a linear or branched C₁-C₅ alkylenegroup.

In some embodiments, a copolymer comprising 1 to 25 mole % of thestructural unit of formula I and 75 to 99 mole % of the structural unitof formula II is provided, wherein R¹ is a linear or branched C₃-C₁₀fluoroalkyl group; R² and R³ are independently at each occurrence ahydrogen, or a methyl group; X is an —O—; Y is a sulfite group or acarboxylate group. The values of m and n are independently at eachoccurrence an integer ranging from 2 to 4. R⁴ and R⁵ are independentlyat each occurrence a linear or branched C₁-C₃ alkyl group; and R⁶ and R⁷are independently at each occurrence a linear or branched C₁-C₅ alkylenegroup.

In some embodiments, a copolymer includes 1 to 10 mole % of thestructural unit of formula I, and 90 to 99 mole % of the structural unitof formula II, wherein R¹ is a linear C₅-C₈ fluoroalkyl group; R², R³,R⁴, and R⁵ are methyl groups; R⁶ is a C₁ alkylene group; R⁷ is a linearC₃ alkylene group; X is —O—; Y is an sulfite group; m is integer 2; andn is integer 1.

In some embodiments, a copolymer is provided, which includes 1 to 10mole % of the structural unit of formula I, and 90 to 99 mole % of thestructural unit of formula II, wherein R¹ is a linear C₅-C₈perfluoroalkyl group; R², R³, R⁴, and R⁵ are methyl groups; R⁶ is a C₁alkylene group; R⁷ is a linear C₃ alkylene group; X is —O—; Y is ansulfite group; m is integer 2; and n is integer 1.

In some embodiments, a copolymer that includes 1 to 10 mole % of thestructural unit of formula I, and 90 to 99 mole % of the structural unitof formula II is provided, wherein R¹ is a tridecafluorohexyl group(—C₆F₁₃); R², R³, R⁴, and R⁵ are methyl groups; R⁶ is a C₁ alkylenegroup; R⁷ is a linear C₃ alkylene group; X is —O—; Y is an sulfitegroup; m is integer 2; and n is integer 1.

In some embodiments, a copolymer comprising structural units derivedfrom a mixture of ethylenically unsaturated monomers comprising 1 to 50mole % of fluoroalkyl monomer of formula III and 25 to 99 mole % ofzwitterionic monomer of formula IV is provided. In formula I, R¹ is alinear or branched C₁-C₃₀ fluoroalkyl group, R² is a hydrogen, or alinear or branched C₁-C₄ alkyl group, X is either an oxygen atom (—O—)or an —NH— group and integer values of m may range from 1 to 5. Informula II, R³ is a hydrogen, or a linear or branched C₁-C₄ alkyl group,X is either an oxygen atom (—O—) or an —NH— group, Y is an anionicgroup, and n is an integer, the value of which may range from 1 to 5. Insome embodiments, R⁴ and R⁵ are independently at each occurrence alinear or branched C₁-C₁₂ alkyl group; a C₅-C₁₂ carbocyclic group, or aC₅-C₁₂ heterocyclic group; and R⁶ and R⁷ are independently at eachoccurrence a linear or branched C₁-C₁₂ alkylene group, a linear orbranched C₂-C₁₂ alkenylene group, a linear or branched C₂-C₁₂ alkylnlenegroup, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclic group. Insome other embodiments, R⁴, R⁵, R⁶, and R⁷ are selected such that atleast two of R⁴, R⁵, R⁶, or R⁷ together with the nitrogen atom to whichthey are attached form a heterocyclic ring containing 5 to 7 atoms.

The anionic group Y may be a sulfonate group (—SO₃ ⁻), a carboxylategroup (—CO₂ ⁻), a phosphonate group (—PO₃ ⁻), a borate group, a borinategroup, a trifluoroboronate group, a sulfinate group, or a phosphinategroup.

In some embodiments, the fluoroakyl monomer of formula I is2-(perfluorohexyl)ethyl methacrylate (i.e., formula V).

In some embodiments, the copolymer comprises structural units derivedfrom a mixture of ethylenically unsaturated monomers comprising 1 to 50mole % of 2-(perfluorohexyl)ethyl methacrylate (formula V) and 25 to 99mole % of zwitterionic monomer of formula VI.

In some embodiments, compositions comprising the above-disclosedcopolymers are provided. The composition comprising these copolymers maybe employed as a coating composition to provide enhanced hydrophilicityand oleophobilcity to surfaces or matrices. Oleophobicity may beimparted by fluoroalkyl groups and hydrophilicity may be imparted byzwitterionic groups of the copolymer.

In some embodiments, a coating composition is provided, which acopolymer comprising 1 to 50 mole % of a structural unit of formula VII;and 25 to 99 mole % of a structural unit of formula VIII, wherein R¹ isa linear C₅-C₈ fluoroalkyl group. Here oleophobicity is imparted to thecoating composition by tridecafluoro hexyl group and hydrophilicity isimparted by sulfobetaine group.

In some other embodiments, copolymer of the coating compositioncomprises 1 to 10 mole % of a structural unit of formula VII, and 90 to99 mole % of a structural unit of formula VIII, wherein R¹ is a linearC₅-C₈ fluoroalkyl group. In some other embodiments, the copolymer of thecoating composition comprises 1 to 10 mole % of a structural unit offormula VII, and 90 to 99 mole % of a structural unit of formula VIII,wherein R¹ is —C₆F₁₃ ⁻. In some example embodiments, a compositioncomprising a copolymer is provided wherein the copolymer comprises astructural unit of formula IX.

The coating composition may further comprise other agents such assolubilizing agents. Suitable solubilizing agents include, but are notlimited to, surfactants, fluorosurfactants or combinations thereof.Further, the coating composition may further comprise solvents orco-solvents. Non-limiting examples of suitable solvents includehexafluoro isopropanol or pentafluorpropanol.

The hydrophilicity and olephobicity of the resulting coating compositionmay be optimized by optimizing the concentration of fluorine atoms inthe fluoroalkyl monomer. For example, for specific water treatmentapplications, optimal levels of hydrophobicity, hydrophilicity andoleophobicity may be achieved by adjusting the wt % of fluorine to about8.4%. However, other factors such as monomer structure (e.g., use oflinear, branched, cyclic perfluorinated or fluorinated alkanes, or chainlength) may further modify the desired hydrophilic and/or oleophobicproperties of the resulting composition.

In some embodiments, membranes comprising a porous substrate andoptionally a coating attached to the porous substrate is provided,wherein at least one of the porous substrate or the coating comprisesany of the disclosed copolymers or copolymeric compositions. Themembrane may further comprise a backing material. In some embodiments,membranes are made of the copolymer. Membranes may be made from thecopolymer by using any of the membrane forming techniques (e.g.,extrusion, injection molding). In some other embodiments, membranescomprise a porous substrate coated with a copolymer composition. Thecopolymer compositions may be disposed on the porous structures byemploying any suitable coating method, for example, by roll-coating,dip-coating (immersion), or spray-coating. The membranes formed from orcoated with the copolymer or copolymer compositions disclosed herein areparticularly useful for removal of oily suspended solids fromproduced/waste water. The copolymer coating renders the resultantmembrane oil-tolerant. During filtration the oil in solution will passthrough the membrane and the copolymer coating prevents the oil fromfouling the membrane and enables the cake of oily solids that builds upon the membrane to be easily washed off.

In some embodiments, a filtration membrane is provided that comprises aporous substrate coated with the copolymeric composition. In someembodiments, the polymeric composition comprises a copolymer comprising1 to 50 mole % of a structural unit of formula VI, and 25 to 99 mole %of a structural unit of formula VII, wherein R¹ is a linear C₅-C₈fluoroalkyl group.

Hydrophilicity and oleophobicity of the coated filtration membrane maybe measured with respect to the contact angle between the filtrationmembrane and a solution. The membrane comprising the polymeric coatingmay have a contact angle of up to about 20° for water, and a contactangle of at least about 60° for a hydrocarbon. In one example, thefiltration membrane has zero contact angle for water and 75° contactangle for hexadecane oil. These coatings may help in efficient removalof oily-solids from the hydrocarbon-contaminated solutions withoutpre-wetting the filtration membrane.

Due to the hydrophilicity imparted by the copolymer coating, the coatedfiltration membrane may be liquid permeable to a sufficient degree forfiltration of aqueous liquids. Hydrophilicity allows passage of waterthrough the membrane without the need for pre-wetting the filter withsolvents such as isopropanol. Coated filtration membrane may retainwater wettability and may be dried and subsequently flow liquid with noprior pre-wetting procedures. The oleophobicity imparted by the coatingsprevents oils in the produced water from wetting the membrane, occludingits pores, and stopping filtration.

The porous substrate may be of a polymeric material. For example, theporous substrate may be made from polytetrafluoroethylene (PTFE),expanded polytetrafluoroethylene (ePTFE), polyolefin, polyester,polyamide, polyether, polysulfone, polyethersulfone, polyvinylidinefluoride, polystyrene, polyethylene, polypropylene, polyacrylonitrile,acrylic and methacrylic polymers, polyurethane, cellulose-basedmaterials or combinations thereof. In one embodiment, the poroussubstrate is formed from ePTFE. In one example embodiment, the poroussubstrate is an ePTFE membrane backed with PTFE.

The porous substrate may have a pore size ranging from about 0.01 micronto about 50 micron. In some example embodiments, the porous substratemay have pore sizes ranging from about 0.01 microns to about 50 microns.In some other embodiments, the pore sizes of the porous substrate mayrange from about 0.1 micron to about 10 microns. In some other exampleembodiments, the pore sizes of the porous substrate may range from about0.3 micron to about 2 microns.

Porous substrate may be made by any method known in the art. Forexample, the porous substrate may made by extruding a mixture ofpolytetrafluoroethylene (PTFE) fine powder particles (e.g., availablefrom DuPont of Wilmington, Del. under the name TEFLON® fine powderresin) and lubricant. The extrudate may then calendared. The calendaredextrudate may then expanded (e.g., sufficiently stretched beyond theelastic limit of the material to introduce permanent set or elongationto fibrils) or stretched in at least one direction to form fibrilsconnecting nodes in a three-dimensional matrix or lattice type ofstructure. Porous substrate may then heated or sintered to reduce andminimize residual stress in the expanded polytetrafluoroethylene (ePTFE)material. However, un-sintered or partially sintered material may alsobe used based on contemplated use of porous substrate. In someembodiments, the size of a fibril that has been at least partiallysintered is in the range of between about 0.05 micron and about 0.5microns in diameter, taken in a direction normal to the longitudinalextent of fibril. Other suitable methods of making a porous substrateinclude, but are not limited to, foaming, skiving, or casting.

In some example embodiments, membranes that comprise an expandedpolytetrafluoroethylene substrate coated with the above-disclosedpolymeric compositions are provided. In some embodiments, expandedpolytetrafluoroethylene substrate is coated with a polymeric coatingcomposition that includes a copolymer comprising 1 to 50 mole % of astructural unit of formula VI, and 25 to 99 mole % of a structural unitof formula VII, wherein R¹ is a linear C₅-C₈ fluoroalkyl group. In someother embodiments, the polymeric coating composition includes acopolymer comprising 1 to 10 mole % of a structural unit of formula VII,and 90 to 99 mole % of a structural unit of formula VIII, wherein R¹ isa linear C₅-C₈ fluoroalkyl group. In some other example embodiments, ahydrophilic-oleophobic membrane is made by coating an expandedpolytetrafluoroethylene substrate with a polymeric coating compositionthat includes a copolymer comprising 1 to 10 mole % of a structural unitof formula VII, and 90 to 99 mole % of a structural unit of formulaVIII, wherein R¹ is a linear —C₆F₁₃.

In some embodiments, the coating composition comprising the copolymermay be reacted with the porous substrate to form a coating disposed onat least one portion of the porous substrate. The copolymer may getbound to the porous substrate through one or more covalent bonds.Covalent bonding may help to avoid extraction of the compound from thefiltration membrane into the solution being filtered. In some otherembodiments, the copolymer may be coated on the porous substrate byphysisorption (e.g., adsorption).

Each porous substrate may be weighed prior to coating and after coatingto establish the desired amount (wt % add-on) of coating material on theresulting membrane filter. The wt % add-on may be calculated from thedifference between the coated membrane weight and the uncoated membraneweight as weight-percent add-on=100*(coated membrane weight−uncoatedmembrane weight)/(uncoated membrane weight). The desired wt % add-on maybe determined from the desired permeability of the membranes aftercoating, and the extent to which the physical properties of the coatinghave been imparted to the membrane. In some embodiments, the wt % add-onmay be as high as 50% (e.g., for making ultrafiltration membranes). Insome other embodiments, the wt % add-on for an un-backed membrane (e.g.,porous substrate made of only ePTFE) may be as high as 20%. In oneexample embodiment, the copolymer may be coated on a porous substratemade of ePTFE backed with PTFE such that the coating constitute to about0.15 wt % to about 5 wt % of the total weight of the resultantePTFE-based filtration membrane. Such membranes may be employed formicrofiltration applications.

Coating composition may be applied to the porous substrate by anysuitable method, for example, by roll-coating, dip-coating (immersion),or spray-coating. The copolymer composition may be coated on to theporous substrate by dissolving it in an appropriate solvent. Forexample, the copolymer may be dissolved in tetrafluoro propanol orhexafluoro isopropanol and this copolymeric solution may be employed forcoating the porous substrate. Coating composition may further includestabilizing agents and/or activators. The coating composition, in asuitable solvent, may be applied to the porous substrate such that thecoating composition passes through the pores and wet-out surfaces of theporous substrate. At least a portion of the porous substrate includingsurfaces of pores may be coated with the coating composition withoutblocking the pores. The coating composition may be then cured by heatingthe porous substrate such that the copolymer flow and coalesce to formcoating onto the porous substrate followed by solvent evaporation.Coatings may be made permanent on the porous substrate by virtue ofeither cross-linking or insolubility in produced water. In oneembodiment, immersion procedure is used to coat the filtration membranewith the coating composition. The copolymer coating composition may beapplied on the porous substrate at low percent loading, for example,about 0.1 to about 1 wt %, to minimize pore constriction. This may varydepending on the weight of the porous substrate as well. In someembodiments, the coating composition include about 0.2 wt % of thecopolymer.

In some embodiments, the filtration membrane may additionally include abacking material. The membrane and the backing materials may beintegrally joined by techniques well known in the art. Non-limitingexamples of backing material include woven or nonwoven syntheticmaterials having the strength necessary to reinforce the filtrationmembrane and the ability to be integrally bound to the membrane whilenot interfering with the passage of permeate through the membrane.Suitable backing materials may include polytetrafluoroethylene,polyester, polypropylene, polyethylene and nylon. In one exampleembodiment, backing material is made of polytetrafluoroethylene.

The porous substrate coated with the copolymeric composition may be usedas a microfiltration membrane or an ultrafiltration membrane. Thecopolymeric coating may render a microfiltration membrane oil-tolerant.By incorporating hydrophilicity and oleophobicity to a microfiltrationmembrane, the copolymer coatings enable filtration of oil-contaminatedproduced water such as is found in unconventional gas and oilproduction. Copolymer-coated microfilters may be employed to reject oilysuspended solids such as dirt and other small particles. In the absenceof such coatings, oil in the produced water (e.g., as emulsified oil)rapidly fouls the membrane and precludes economic operation.Oil-tolerant microfilters pass oil-droplets and dissolved oil withoutbeing fouled by them. The copolymeric coating may also render anultrafiltration membrane oil-tolerant and oil-rejecting. Coatedultra-filters, being oleophobic, reject oil droplets to avoid beingfouled by the oil.

Oil-tolerant, hydrophilic microfiltration or ultrafiltration membranefilters described herein have significant advantages over currentlyavailable hydrophilic, non-oil-tolerant microfiltration filters. Some ofthese include, but are not limited to, (a) elimination of pre-wettingthe membrane with flammable solvents such as isopropanol, (b) thecapability of the membrane to used effectively with a wide range ofproduced water compositions, (c) easier, milder and less frequentcleaning requirements, (d) Smaller footprint requirements in comparisonwith biocide treatment facilities, and (e) elimination of the need fortoxic chemical storage and handling (e.g. biocides and solvents) infield operations, which are usually in remote locations.

In some embodiments, methods for treating contaminated water using suchfiltration membranes are provided. The contaminated water may be thewater produced from oil-sands, coalbed methane, unconventional gas,enhanced oil-recovery, salt-water aquifers, or mining processes. Thecontaminated water may have oil in a dispersed phase and water is acontinuous phase. For example, the contaminated water may be theproduced water from the petroleum industries, the produced water in theproduction of conventional or unconventional natural gas, or shalegas-produced water. The contaminated water may often contain a mixtureof water and hydrocarbon (e.g., oil) and may further comprise oilysuspended particles and high levels of dissolved solids (e.g., dissolvedsalts). For example, the contaminated water may contain organiccomponents in a range between 1 and 1000 ppm. Further, for example, itmay contain free un-dissolved oil in a range between 1 and 500 ppm,dissolved solids in a range between 500 and 200000 ppm, and suspendedparticles in a range between 1 and 2000 ppm.

In some embodiments, a method of treating contaminated water using theabove-disclosed filtration membrane is provided. The method includes thesteps of providing the contaminated water comprising water and oil,providing a filtration membrane comprising the copolymeric coatingdescribed herein and passing the contaminated water through the membraneto generate treated water. For example, the contaminated water may befiltered through the membrane comprising the copolymeric coating todecontaminate the water. Upon passing through the membrane, theconcentration of the suspended particles is decreased.

In some embodiments, the filtration membrane may be used for method ofseparating oily particles from a mixture comprising water and oil. Themethod includes contacting the mixture with the filtration membrane andfiltering the mixture through the filtration membrane. After filtration,oily particles in the mixture may be separated by the filtrationmembrane and water and oil may pass through the pores. However, the oilin water may not foul the coated membrane due to its oil-tolerance.Further, the removal of cake generated by the filtered oily particlesmay be easily removed from the membrane due to its oleophobiccharacteristics. The filtration and subsequent separation may beperformed under gravity.

The following examples are disclosed herein for illustration only andshould not be construed as limiting the scope of the invention. Someabbreviations used in the examples section are expanded as follows:“mg”: milligrams; “ng”: nanograms; “pg”: picograms; “fg”: femtograms;“mL”: milliliters; “mg/mL”: milligrams per milliliter; “mM”: millimolar;“mmol”: millimoles; “pM”: picomolar; “pmol”: picomoles; “μL”:microliters; “min.”: minutes, “gal”: gallons “gpm”: gallons per minute;“gm”: grams and “h.”: hours.

EXAMPLES Example 1 Synthesis of copolymer of2-(methacryloyloxy(ethyl)dimethyl-(3-sulfopropyl) ammonium hydroxide(SBMA) and 2-(Perfluorodechexyl)ethyl methacrylate

The copolymer was prepared by the free radical polymerization ofzwitterionic, [2-(methacryloyloxy(ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA, formula VI) and 2-(Perfluorodechexyl)ethylmethacrylate (DuPont™'s fluorinated Capstone 62MA™, formula V) using2,2′-Azobis(2,4-dimethyl)valeronitrile (Vazo-52) as an initiatior. SBMAand Vazo-42 were dissolved in 85% ethanol and 15% water. The Capstone62MA™ monomer was added to this solution and the solution de-oxygenatedand stirred for 30 minutes. The solution was then heated to about 50° C.When the reaction mixture temperature was about 50° C., the Capstone2MA™ monomer was dissolved making the reaction mixture clear. Shortlythereafter, Vazo-52 decomposition initiated polymerization. The reactionwas allowed to continue as the copolymer began to precipitate until theprecipitation caused the stiffing to stop. The copolymer was thenseparated from the unreacted supernatant, dissolved in 20 wt % inhexafluoro-2-propanol (HFIP), and precipitated in methanol. NMR showedcopolymerization of both monomers and no residual unreacted monomerswere found in the precipitate.

The z90 copolymer was prepared by the free radical polymerization of 90mole % of zwitterionic SBMA (formula VI) and 10 mole % of2-(Perfluorodechexyl)ethyl methacrylate (formula V) using2,2′-Azobis(2,4-dimethyl)valeronitrile (Vazo-52) as an initiatior asdescribed above.

Example 2 Coating composition comprising the copolymer of2-(methacryloyloxy(ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide and2-(Perfluorodechexyl)ethyl methacrylate

The precipitated copolymer in Example 1 was again dissolved in HFIP togenerate the coating composition. Glass chips were spin-coated with thiscopolymer composition and were used for contact angle measurements. Thecontact angles for water and hexadecane measured on these copolymercoated glass chips (by placing 1 μL of solvent) were near 0°-10°, and75° respectively. The low water contact angle evolved over a fewminutes, presumably due to surface rearrangement of the hydrophiliccomponent of Z90 copolymer.

Example 3 Coating of ePTFE/PTFE Membrane Using the Coating CompositionComprising the Copolymer of2-(Methacryloyloxy(Ethyl)Dimethyl-(3-sulfopropyl)ammonium hydroxide and2-(Perfluorodechexyl)ethyl methacrylate

Filtration membrane was prepared by dip-coating 2.5-inch diameter disksof 1.5 μm ePTFE/PTFE membrane in a 0.2 wt % solution of the copolymer ofExample 1 in HFIP. Excess solution having copolymer composition wasremoved by passage through a nip roller followed by HFIP evaporation.Each treated filtration membrane was weighed prior to coating and afterdrying to establish the desired amount (wt % add-on) of coating materialon the filter. The wt % add-on is calculated from the difference betweenthe coated membrane weight and the uncoated membrane weight asweight-percent add-on=100*(coated membrane weight−uncoated membraneweight)/(uncoated membrane weight). The desired wt % add-on may bedetermined from the desired permeability of the membranes after coating.A 0.2% solution of the copolymer of Example 1 resulted in 0.15 wt %add-on to the ePTFE/PTFE membrane.

Example 4 Treatment of Contaminated Water with ePTFE/PTFE MembraneCoated with the Copolymer of2-(Methacryloyloxy(Ethyl)Dimethyl-(3-sulfopropyl)ammonium hydroxide and2-(Perfluorodechexyl)ethyl methacrylate

A batch of test, contaminated water consisting of 20 wt % produced waterfrom the Utica shale play and 80 wt % from the Barnett shale play wasplaced in a pressurized feed vessel with a magnetic stir bar foragitation. The produced water used for these tests had approximately 600mg/L total suspended solids. A filtration membrane coated with the Z90copolymer of Example 1 (1.5 micron ePTFE membrane on PTFE backing) wasplaced in a Millipore High Pressure Filter Holder (Millipore XX4504700).The filter holder assembly was placed in a test rig comprising thepressurized feed tank, the filter holder, a mass flow meter, pressuretransducers upstream and downstream of the filter holder, and a filtratereceiver tank. The filtration membrane was conditioned by pumping 300 mL13.2 wt % NaCl solution in water through the filter at about 25 gm/min.After conditioning, the filtration membrane was placed into service withthe produced water mixture. The upstream pressure was 3 bar gage, andthe downstream pressure was atmospheric pressure. The system wasoperated in this manner until the flux rate dropped below 0.46 gpm/ft².At this point, the filtration membrane was backwashed by pumpingfiltrate backwards through the filtration membrane, and the sludge wasdrained from the filter holder feed chamber by gravity. A total of threefilter-backwash cycles were completed. Same procedure was repeated witha control filtration membrane, CE-1 (1.5 μm ePTFE/PTFE membrane withoutZ90 copolymer coating).

The performance of the copolymer coated membrane and the controlmembrane is illustrated in Table 1. At a pressure differential of 1 bar,the Z90 copolymer-coated filter significantly out-performed the controlfilter with respect to total flux consistency (0.67 for Z90 vs. 0.19 forthe control). At a pressure differential of 3 bar, for three cycles, theaverage cycle time for Z90 copolymer-coated filter was 39 minutes, theaverage flux was 1.0 gpm/ft², and the total flux consistency was 0.17.The total flux consistency is defined as the ratio of the total flux(gal/ft²) in the third cycle divided by the total flux in the firstcycle. The average flux, the average cycle time, and the total fluxconsistency were significantly lower for the uncoated filtrationmembrane in comparison with the filtration membrane coated with Z90copolymer composition of Example 1.

TABLE 1 Performance of 1.5 μm ePTFE/PTFE filtration membranes Total Wt %Flux Consistency: Add-on Avg Total Flux cycle-3 (vs. Avg Flux Cycle(gal/ft²)/ ΔP, filter 3 cycles, Time, Total Flux cycle-1 bar Exampleweight) gpm/ft² minutes (gal/ft²) 3 Z90-Coated 0.17 1.0 39 0.17 MembraneCE-1 — 0.58 12 0.01 1 Z90-Coated 0.16 0.90 1.4 0.67 Membrane CE-1 — 0.941.3 0.19

Table 2 shows the cumulative flux and cycle time results for the filterstested at 3 bar differential pressure.

TABLE 2 Cumulative flux and cycle time of 1.5 μm ePTFE/PTFE filtrationmembranes Cycle 1 Cycle 2 Cycle 3 Cu- Cu- Cu- mulative Cycle mulativeCycle mulative Cycle Filter Flux Time Flux Time Flux Time Treatment(gal/ft²) (min) (gal/ft²) (min) (gal/ft²) (min) Z90-Coated 76.8 72.933.7 31.7 11.3 12.0 Membrane CE-1 29.3 28.8 4.4 6.2 0.4 0.800

Throughout the specification, exemplification of specific terms shouldbe considered as non-limiting examples. The singular forms “a”, “an” and“the” include plural referents unless the context clearly dictatesotherwise. Approximating language, as used herein throughout thespecification and claims, may be applied to modify any quantitativerepresentation that could permissibly vary without resulting in a changein the basic function to which it is related. Accordingly, a valuemodified by a term such as “about” is not to be limited to the precisevalue specified. Unless otherwise indicated, all numbers expressingquantities of ingredients, properties such as molecular weight, reactionconditions, so forth used in the specification and claims are to beunderstood as being modified in all instances by the term“about.”Accordingly, unless indicated to the contrary, the numericalparameters set forth in the following specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained by the invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. Where necessary, ranges have beensupplied, and those ranges are inclusive of all sub-ranges therebetween.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The above detaileddescription is exemplary and not intended to limit the invention of theapplication and uses of the invention. Furthermore, there is nointention to be limited by any theory presented in the precedingbackground of the invention or the above detailed description. Theforegoing embodiments are selected embodiments or examples from amanifold of all possible embodiments or examples. The foregoingembodiments are therefore to be considered in all respects asillustrative rather than limiting on the invention. While only certainfeatures of the invention have been illustrated and described herein, itis to be understood that one skilled in the art, given the benefit ofthis disclosure, will be able to identify, select, optimize or modifysuitable conditions/parameters for using the methods in accordance withthe principles of the invention, suitable for these and other types ofapplications. The precise use, choice of reagents, choice of variablessuch as concentration, volume, incubation time, incubation temperature,and the like may depend in large part on the particular application forwhich it is intended. It is, therefore, to be understood that theappended claims are intended to cover all modifications and changes thatfall within the spirit of the invention. Further, all changes that comewithin the meaning and range of equivalency of the claims are intendedto be embraced therein.

The invention claimed is:
 1. A method of treating a contaminated watercomprising: providing the contaminated water comprising water and oil;providing a membrane comprising a porous substrate and a coatingattached to the porous substrate, wherein at least one of the poroussubstrate or the coating comprises a copolymer comprising 1 to 10 mole %of a structural unit of formula I; and 90 to 99 mole % of a structuralunit of formula II,

wherein R¹ is a linear or branched C₁-C₃₀ fluoroalkyl group; R² and R³are independently at each occurrence a hydrogen, or a linear or branchedC₁-C₄ alkyl group; either R⁴ and R⁵ are independently at each occurrencea linear or branched C₁-C₁₂ alkyl group, a C₅-C₁₂ carbocyclic group, ora C₅-C₁₂ heterocyclic group, and R⁶ and R⁷ are independently at eachoccurrence a linear or branched C₁-C₁₂ alkylene group, a linear orbranched C₂-C₁₂ alkenylene group, a linear or branched C₂-C₁₂ alkynlenegroup, a C₅-C₁₂ carbocyclic group, or a C₅-C₁₂ heterocyclic group, or atleast two of R⁴, R⁵, R⁶, or R⁷ together with the nitrogen atom to whichthey are attached form a heterocyclic ring containing 5 to 7 atoms; X isindependently at each occurrence an —O— or —NH—; Y is a sulfite group ora carboxylate group; and m and n are independently at each occurrence aninteger ranging from 1 to 5; and passing the contaminated water throughthe membrane to generate a treated water.
 2. The method of claim 1,wherein the contaminated water is a produced water.
 3. The method ofclaim 1, wherein the contaminated water comprises total organiccomponents in a range between 1 and 1000 ppm.
 4. The method of claim 3,wherein the contaminated water comprises free un-dissolved oil in arange between 1 and 500 ppm, total dissolved solids in a range between5000 and 200000 ppm, and total suspended solids in a range between 1 and2000 ppm.
 5. The method of claim 4, wherein the concentration of thesuspended solids in the treated water is lower than that of thecontaminated water.
 6. The method of claim 1, wherein the copolymercomprises 1 to 10 mole % of a structural unit of formula VII, and 90 to99 mole % of a structural unit of formula VIII, wherein R¹ is a linearC₅-C₈ fluoroalkyl group; and


7. The method of claim 6, wherein the porous substrate has a pore sizeranging from about 0.01 micron to about 50 micron.
 8. The method ofclaim 6, wherein the porous substrate comprises a polymer selected fromthe group consisting of polytetrafluoroethylene, expandedpolytetrafluoroethylene, polysulfone, polyethersulfone, polypropylene,polyvinylidine fluoride, polyamide, polystyrene, polyethylene,polyacrylonitrile, cellulose-based materials and combinations thereof.9. The method of claim 6, wherein the porous substrate is expandedpolytetrafluoroethylene.
 10. The method of claim 6, wherein thecopolymer comprises 10 mole % of the structural unit of formula VII, and90 mole % of the structural unit of formula VIII.
 11. The method ofclaim 10, wherein R¹ of the copolymer is —C₆F₁₃.